Twenty-five protesters were arrested Monday after they chained themselves to doors and a flagpole at the Oakland Police Department headquarters.

The demonstrators were protesting killings by police in New York and Missouri, including the slayings of Eric Garner and Michael Brown.

A live-stream video via Blackout Collective shows demonstrators blocking a doorway outside the headquarters and singing, “Calling out the violence of the racist police” as they were taken into custody by officers.

Oakland police said Monday afternoon that 25 people had been arrested on suspicion of obstructing and blocking a public safety building and delaying a police officer.

One protester climbed a flagpole and raised a banner, which protesters said commemorated men and women killed by police. Protesters chained shut four of the building's entrances and then chained themselves to the doors.

"Three of these doors are our main ingress and egress for the public and Oakland Police Department personnel," police said in a statement. "As a result, the public could not access important police services, such as reporting crimes, obtaining public records, accessing necessary paperwork for vehicle impound releases and property releases."

Using a pair of cutters, officers cut chains from the protesters and removed them from the front doors of the police headquarters, which had been sealed shut.

A woman filming the demonstrations said on live video that 100 protesters had been marching through the rain-soaked streets of Oakland since 7:30 a.m. She tweeted, "I repeat OPD is shut down!!!"

Protesters block Oakland police headquarters

Demonstrators block traffic in Oakland and the entrance to the city's police headquarters.

Demonstrators block traffic in Oakland and the entrance to the city's police headquarters.

Elsewhere, Oakland police said a dozen protesters were chained to one another and were blocking the intersection of Broadway and 7th Street. Protesters also were chained together on the northbound Interstate 880 at Broadway, closing access to the freeway ramp.

The Oakland police's hostage negotiating team was on hand to deal with protesters.

The Bay Area Solidarity Action Team said in a statement that the 4 1/2-hour blockade at police headquarters -- in which protesters separated themselves into race-based groups including black, white and Asian -- was a demand for “an end to racist violence against the black community.”

“Silence is violence,” said Felicia Gustin. “The abusive treatment of people of color by the police is a moral crisis for our country and our city, and we cannot turn a blind eye any longer. It is time for white people to join with black communities to end the war on black people."

The protest follows a series of arrests made during weekend demonstrations.

On Saturday, a crowd of about 3,000 marched peacefully in downtown Oakland but after most of the crowd dispersed, police said they received reports of vandalism, broken windows and small fires. At least 45 demonstrators were arrested for various crimes, including vandalism, resisting arrest and failure to disperse, police said.